The subject invention is directed to an improved modular multilevel raised floor electro-mechanical distribution system for installation in building structures including, but not limited to, data centers and similar rooms having high heat loads requiring usually dedicated cooling systems and usually having extensive data cabling and wiring. In addition to a walking and equipment support surface, the invention provides dedicated levels, isolated from one another and positioned under the walking surface, for distribution of electrical services, including data, on the one hand, and conditioned air, on the other. As is discussed further below, the present invention represents a significant advance over the inventor's pioneering “Modular Combination Floor Support and Electrical Isolation System for Use in Building Structures,” which was described and claimed in Reissue Pat. No. 33,220, and which was made the subject of the successful broadening reissue application during the inventor's litigation for willful patent infringement, Collier, et al. v. Airtex, Inc., et al., 87 C 4097 (N.D. Ill. 1990), aff'd, 968 F2d 1227 (Fed. Cir. 1992), in which the inventor prevailed on all counts against the defendants. The title “Modular Multilevel Raised Floor Electro-Mechanical Distribution System” is used herein to refer to the invention because it more accurately reflects the invention's multiple functions than does the term used in the RE 33,220 patent. In the discussion that follows, the invention will sometimes be referred to as “the system.”
Turning now to the specific problems that are either ineffectively addressed by—or are in fact caused by—the prior art, and to which the present invention is directed, it is to be noted that there is a universal, long-felt need among the designers of data centers and similar facilities for an effective, efficient, system for delivering and managing conditioned air and electrical services in such rooms. Energy efficient, uniform, and dependable distribution of air conditioning has become especially important given the fact that in just the past 10 years the average data center heat load has risen from approximately 20 to 40 watts per square foot to between 80 and 120 watts per square foot
Of course, over the same period, the cost of electricity has skyrocketed and its availability in some regions has become less dependable. It is generally recognized by energy experts that the electricity required for data center operations just in the United States is equal to the output of twelve average size power plants. Put another way, it is estimated that data centers consume 1.5% of all the electrical power consumed nationally, and that 45% of this electricity is used to generate data center cooling. Put another way, it is estimated that data centers consume 1.5% of the total U.S. electricity consumption (61 Billion kWh in 2006), “EPA Report to Congress on Server and Data Center Energy Efficiency,” p. 4, Aug. 2, 2007. Moreover the U.S. consumption is only 40% of the worlds data center consumption, as stated in “Estimating Regional Power Consumption Servers: A Technical Note,” by Jonathan G. Koomey, Ph.D. Project Scientist, Lawrence Berkeley National Laboratory. p. 1. 45% of this electricity is used to generate data center cooling. See also, The Green Grid, “Guidelines for Energy Efficient Data Centers,” p. 3, FIG. 1, Feb. 16, 2007.
And, as difficult to believe as it may be, credible current estimates are that the average data center heat load may rise to between 400 and 500 watts per square foot in the next three to five years! This is likely to occur even if progress is made in developing computer equipment that generates less heat, because of the widely expressed goal of engineers, for both security and economic reasons, of reducing significantly the typical data center footprint while at the same time increasing greatly the density of the computer equipment housed within the space.
Of course, in data center and similar high-heat environments, air conditioning is not a mere luxury that can be skimped on or dispensed with. Overheated computers and other electronic equipment can result in system wide failure, permanent data loss, and extensive hardware damage.
Yet, except where the inventor's original invention is being used, the method for distributing air conditioning and electrical conductors in data centers and similar facilities remains the same as it has for over 40 years, namely, routing the disparate electrical and mechanical services through the undifferentiated space under the conventional raised access floors so familiar to those skilled in the art. Such single-level raised access floors comprise a grid work of pedestals positioned on a building floor, the tops of which pedestals support the corners of access floor panels. These panels are usually square and measure approximately 24″×24″, or a close metric equivalent, and are positioned next to one another on the pedestal grid using a gravity fit. “Cable cut-outs” are made in various panels to permit the passage of electrical conductors from the space under the access floor to equipment sitting on it. Perforated access floor panels are provided to permit, at least theoretically, conditioned air to enter the space above the floor for purposes of cooling computer and associated equipment. To add required stability to the single-level access floor structure, stringers often to tie the pedestal heads together. The inherent problems the conventional raised access floors create for air distribution, cabling and wiring management, and room reconfiguration are present right from the moment facility operations begin and become progressively worse as time goes on.
With respect to conditioned air distribution, blowing chilled air under a single-cavity raised floor is an extremely inefficient way of delivering essential cooling to the computer equipment sitting on the floor surface. Even when oversize package down-flow air handling units are used, or “extra” units are added to the data center plan, air distribution is inadequate. It is often claimed that adding air conditioning capacity far in excess of what should actually be needed to meet a data center's heat load is wise because it provides back-up or “redundant” coverage in case one of the other package units fails. This alleged protection, however, is illusory.
To understand why, one must first understand that under floor air distribution in a typically designed data center is wholly dependent on the “throw distance” achievable by an down-flow unit's fan. Under ideal conditions, which virtually never exist as is explained further below, a down-flow air conditioner can throw the conditioned air it generates a distance of about 30 feet in a pie-slice shaped pattern under a raised floor. The force generated by the fan is supposed to push the cool air under the floor and up through the single level raised floor's perforated panels to cool the directly adjacent computer equipment.
Valuable interior room space must be dedicated to the placement of the down-flow air handlers in order to provide the theoretical room area coverage. This is because there can be no effective pressurization of the under floor space, as is explained further below. Even under ideal conditions, if a unit fails the region that is supposed to be cooled by it will quickly become starved for conditioned air unless there is a so-called “redundant” down-flow air handler sitting right next to it. This will rarely, if ever, be the case because as anyone familiar with data center operations knows, all of the air conditioners, including the supposedly redundant one, are spaced apart from each other in order to achieve the best room area coverage possible under the circumstances. The reality is that any supposedly “backup” or “redundant” unit is switched on and used continuously along with the rest of the room's air conditioners.
Room designers know that the package down-flow air handlers will not provide the theoretical 30 foot throw distance under practical working conditions. For one thing, “ . . . 25% of the air flow in the raised floor passes through cable cutouts, cracks between the [access floor] panels and other leakage areas. See, Liebert Corporation, “Installation Manual, Liebert Deluxe System/3™—Chilled Water, 50 and 60 Hz, 2-60 Ton CW Systems (FH/VH),” p. 18, copyright 2006. Other such “leakage areas,” which are often far from where conditioned, moving air is needed to cool equipment, include the large openings that are created whenever floor panels are removed so that cables, wires, and chilled-water pipes under the floor can be accessed.
In addition, the movement of conditioned air is thwarted by the blockages created by these cables, wires, wire-ways, and piping. Frequently, old, unused cables and wire-ways are not removed from under a conventional raised floor. Among the reasons for this are that removing too many floor panels, and the associated stringers where they are present, compromises a conventional raised floor's stability. Moreover, data center managers know that lifting panels in order to remove old conductors and wire ways exacerbates the already serious airflow problem by permitting the escape of conditioned air. In addition, it is uncomfortable to work in the dirty, drafty, and cold under-floor environment where the electrical conductors are often several feet below the surface of the walking surface—at least at first. In its worst, but all-too-common, manifestation the under floor congestion eventually results in cables, most of which are no longer in use, actually pushing raised floor panels off of their support pedestals.
The blockages stop conditioned air from going where it is supposed to, which often causes the package air handling units to “short circuit.” This means that instead of traveling to equipment and carrying away heat, the conditioned air discharged by an air conditioner's supply side is immediately sucked back into the unit's return side. As explained by Intel, “[w]hen we started measuring data center heat densities, we were amazed to discover how inefficient our cooling methods were. Our computer rooms air conditioning (CRAC) units were moving huge quantities of air, yet their cooling coils were only providing 10 to 25 percent of their rated capacity. There were localized hot spots within the data center and some servers were ineffectively drawing in hot air from the hot aisles. Other areas were very cold, with most of the air bypassing the hot equipment and short circuiting right back to the CRAC units.” Intel Information Technology, White Paper, Air-Cooled High-Performance Data Centers: Case Studies and Best Methods, November 2006, p. 4.
The fact is that the air distribution balance is so poor in many facilities that hot air from the room is drawn downward by the Venturi effect through some of the very perforated panels that are supposed to be delivering cool air. It is the combination of leaks and blockages that makes it impossible to pressurize the under floor space so as to provide adequate, uniform, and predictable air delivery.
Yet another dysfunctional feature that hinders effective air conditioning and wastes energy in data centers using package down-flow units is “duty cycling.” While some of the units are in cooling mode others are in heating mode to provide the proper humidity for the room. This means that the units often operate at cross purposes to one another.
To cope with the universal problem that the data center industry calls “hot spots,” i.e., severely overheated equipment areas, data center operators are reduced to using large pedestal fans and movable spot coolers, which consume additional electricity, take up space, and add their own heat to the room that needs cooling. Hot spots exist in data centers having conventional raised access floors even when air conditioning capacity is far in excess of what should be required to address a room's heat load. There can also be “cold spots,” which can also affect computer equipment functioning, and certainly constitute a waste of energy. The situation is primitive, costly, and dangerous.
The existence of these problems is not a matter of serious dispute and data center energy consumption and waste, including the energy used to generate air conditioning, have been a major focus of both government and private industry concern. Thinking and building “Green” have become the watchwords of the data center industry.
It is not surprising, therefore, that various means have been proposed for coping with the energy waste and other problems associated with data center air conditioning. For example, a number of manufacturers have begun to offer special equipment enclosure cabinets having chilled water pipes in them to cool the enclosed equipment. These cabinets can cost upwards of $30,000 a piece. It becomes quite apparent that this is a costly solution indeed, when one considers the fact that a moderately sized data center may house as many as several hundred equipment cabinets.
The Intel document sited above suggests a number of different attempts to solve the problems with cooling equipment in data centers. One such recommendation is to construct a two-story data center that has the air conditioning and other equipment in the lower story and the equipment in the upper story with the air being fed through the floor slab. A second recommendation is to build passive chimney cabinets from the raised floor to the ceiling to try and contain the air so it can't short circuit. Another recommendation is to build a room without a raised floor and bring all the supply air to the cold aisles through metal ductwork, yet another recommendation is to use a combination of the passive chimney cabinets with wall supplied air handling units that feed the air under a raised floor and return the warm air through a ceiling plenum.
The ASHRAE Journal, December 2007, p. 41 suggests a High-density Heat Containment System Architecture, It uses a rack enclosure concept, and a physical barrier to contain the IT equipment heat and provide a predictable pathway for the heat to return to the data center cooling system. This was actually done at Oracle in 2004, they have large flexible ducts extending from the top of the equipment cabinets to the return ceiling plenum.
Although the present invention does not preclude the use of at least some of these prior art approaches to curing the deficiencies of standard access floor conditioned air distribution, e.g., water-cooled equipment cabinets, and the ORACLE heat containment method, for the reasons discussed below it is believed that it will render them generally unnecessary.